U.S. Pat. No. 8,131,930 discloses a technique in which a SSD (Solid State Drive) is installed instead of a HDD (Hard Disk Drive), and a portion of the SSD is used as a cache. By configuring a large capacity cache using non-volatile memory, the power consumption of the cache can be reduced. On the other hand, in the event that a cache configured using non-volatile memory is stolen or lost, there is a danger of data leakage.
Accordingly, methods of encrypting data stored in a cache configured using non-volatile memory have been proposed (PTL 2). Data can in this way be encrypted and stored in non-volatile memory used as a cache, and thus the data can be protected.